The Immunogenicity of SARS-CoV-2 Vaccines in Thai Patients with Rheumatoid Arthritis: A Cross-Sectional Study from the National Health Thailand Program
Tanapon Ussanawarong, MD1, Ajanee Mahakkanukrauh, MD1, Chingching Foocharoen, MD1, Siraphop Suwannaroj, MD1, Patnarin Pongkulkiat, MD1, Piroon Mootsikapun, MD2, Atibordee Meesing, MD2, Supranee Phanthanawiboon, PhD3, Sira Nanthapisal, MD4
Affiliation : 1Division of Rheumatology, Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, 2Division of Infectious Diseases and Tropical Medicine, Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, 3Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, 4Division of Pediatric Allergy and Immunology, Department of Pediatrics, Faculty of Medicine, Thammasat University, Pathumthani, Thailand
Background: Patients with rheumatoid arthritis (RA) on immunosuppressive therapy may exhibit weaker and less durable vaccine responses compared to the general population. Thailand offers diverse SARS-CoV-2 vaccines, but the immune response among Thai RA patients to different vaccine regimens remains unclear.
Objective: The authors aimed to investigate the COVID-19 spike protein IgG antibody level after completing the Thai SARS-CoV-2 vaccine program in Thai RA patients and to identify factors associated with low immunogenicity.
Materials and Methods: A cross-sectional study was conducted between January 2022 and February 2023 at the rheumatology clinic, Srinagarind Hospital, Khon Kaen University. Adult RA patients who completed the Thai SARS-CoV-2 vaccine program were tested for spike protein IgG antibody levels 28 to 90 days after their second dose. Demographic data, disease activity, and medications were recorded.
Results: Twenty-five RA patients were included, with 84% being female and a mean age of 61.1 years. Most patients received methotrexate (64%) and prednisolone (72%). The overall median (IQR) spike IgG antibody level was 407.7 U/ml (79.3 to 1,190). Only one patient (4%) had low immunogenicity (10.1 U/ml), who received the AstraZeneca–Pfizer regimen. The highest median antibody level was found in the Sinovac–Pfizer group (4,376 U/ml), and the lowest was in the Sinopharm–Sinopharm group (21.2 U/ml). Among the four matched RA–control pairs, the antibody levels were generally comparable.
Conclusion: After completing two doses of the SARS-CoV-2 vaccination, Thai RA patients demonstrated good immunogenicity. Their IgG levels appeared comparable to those of healthy controls. Further studies with larger populations are warranted to confirm these findings and explore factors contributing to low immunogenicity.
Keywords : Rheumatoid arthritis; SARS-CoV-2; Vaccine; Immunogenicity; Thailand; DMARDs; Methotrexate; Biologic therapy
